1. Field of the Invention
This invention relates to a method for refining an easily polymerizable matter-containing substance and an apparatus therefor. More particularly, it relates to a method for refining (meth) acrylic acid and/or a (meth) acrylic ester while preventing the acid and/or the ester from being polymerized particularly in the vapor phase and an apparatus to be used therefore.
2. Description of the Related Art
Such an easily polymerizable matter as impurities-containing (meth)acrylic acid has been heretofore refined as follows.
In a distillation column with a condenser and a re-boiler, the condenser is connected to the top of the distillation column via a (inter) connecting line and the re-boiler is positioned near the lower part of the distillation column via a (inter)connecting line. Here, the feed material such as the impurities-containing (meth)acrylic acid is supplied to the distillation column and distilled therein. The vapor distilled from (meth)acrylic acid which has entered the condenser via the connecting line is condensed and apart thereof is returned to the distillation column and the rest thereof is recovered as distillate D or subjected further to a subsequent treatment. Meanwhile, the liquid containing (meth)acrylic acid through the bottom of the distillation column is supplied to the re-boiler and reboiled therein, with the result that the vapor containing (meth) acrylic acid will be returned via the connecting line to the distillation column.
It is well known that (meth)acrylic acid and/or a (meth)acrylic ester is so easily polymerized very often during the process of production such as refinement and that the apparatus of production compellingly stopped. As a measure, the practice of adding a polymerization inhibitor such as hydroquinone or phenothiazine during the production of (meth)acrylic acid and/or (meth)acrylic ester thereby preventing polymerization in the liquid phase of the purification process has found popular recognition.
U.S. Pat. No. 3,988,213 discloses a method for preventing the vapor of a vinyl compound from condensing or polymerizing by providing a distillation column with a jacket.
Further, U.S. Pat. No. 3,717,553 discloses a distillation column which, by having an opening formed near the wall of a tray tower and consequently allowed to have the wall of its own wetted, is enabled to prevent a vinyl monomer from polymerizing.
Perfect prevention of the polymerization that occurs during the distillation of an easily polymerizable matter or during the condensation of a vapor or the re-condensation of the vapor in a vapor phase has not yet been accomplished.